2026 Proffered Presentations
S118: AUTONOMIC NERVE FIBER COMPOSITIONS OF LACRIMAL AND ZYGOMATICOTEMPORAL NERVES: A CADAVERIC IMMUNOHISTOCHEMICAL ANALYSIS
Hangil Lee, MD1; Bushra Rhaman, MD2; Kelly Shaftel, MD1; Hassan Fadel, MD1; Jacob Pawloski, MD1; Jack Rock, MD1; John Craig, MD3; 1Department of Neurosurgery, Henry Ford Hospital; 2Department of Ophthalmology, Henry Ford Hospital; 3Department of Otolaryngology, Henry Ford Hospital
Introduction: The vidian nerve (VN) has been considered the predominant source of parasympathetic innervation to the lacrimal gland. The VN has been shown to supply the lacrimal gland via the zygomaticotemporal nerve (ZTN), a branch of V2 from the pterygopalatine fossa, which enters the orbit via the inferior orbital fissure (IOF). While rare overall, xerophthalmia may occur when the VN is transected during certain endoscopic sinonasal and skull base surgeries. This would imply that the lacrimal gland receives an alternative source of autonomic innervation, but very few studies have explored this possibility.
Objective: To analyze and compare lacrimal nerve (LN) and ZTN sympathetic and parasympathetic nerve fiber compositions via tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) staining, respectively.
Methods: Bilateral frontoorbital craniotomies were performed on 9 fresh injected cadaver heads. Approximately 1 cm sections of the LN and ZTN were harvested from one orbit per cadaver. The LN was sectioned at its entry into the orbital apex through the superior orbital fissure, and the ZTN was sectioned at its orbital entry through the IOF. The samples were formalin-fixed, sectioned, and underwent immunofluorescent staining for ChAT and TH. Areas of positive marker staining were measured and expressed as percentages of total tissue area per specimen. ChAT and TH percent areas, and variance, were compared within and between nerve specimens.
Results: ChAT percent area was significantly greater in ZTN compared to LN specimens (24.6% versus 14.1%, p =0.004). TH percent area was similar between ZTN and LN specimens (3.7% versus 3.8%, p = 0.883). ChAT percent area was greater than TH in both ZTNs (p = 0.0003) and LNs (p = 0.026). Additionally, both ChAT and TH percent areas demonstrated high variance across LNs and ZTNs (CV > 0.3), and their degrees of variance were similar to one another in each nerve type (p>0.172). Lastly, ChAT and TH variances were each equivalent between LNs and ZTNs (p>0.121).
Conclusions: While sympathetic and parasympathetic nerve fiber proportions demonstrated considerable variability across nerve specimens, there were generally more parasympathetic fibers in ZTNs than LNs. ZTN may be the dominant parasympathetic supply to the lacrimal gland, but additional contribution from the LN could explain why so few patients develop xerophthalmia following vidian neurectomy. As a corollary, perhaps lower LN parasympathetic fiber density in some patients could account for xerophthalmia development after vidian neurectomy.
Keywords: Lacrimal nerve; Zygomaticotemporal nerve; Choline acetyltransferase (ChAT); Tyrosine hydroxylase (TH); Autonomic innervation; Cadaveric study
